Leetcode 68. 文本左右对齐

先判断一行最多有几个单词，之后计算单词之间空格个数，再组合

class Solution {
public:
    vector<string> fullJustify(vector<string>& words, int maxWidth) {
        int _n = words.size(), l = 0, r = 0, w_n;
        vector<string> ans;
        string str;
        if (!_n) return ans;
        while (r < _n) {
            l = r, w_n = words[r].size();
            while (w_n <= maxWidth && ++r < _n) w_n += 1 + words[r].size();
            if (r == _n) {
                str = words[l];
                for (int k = 1; k + l < r; ++k)
                    str += ' ' + words[l + k];
                str += string(maxWidth - str.size(), ' ');
                ans.push_back(str);
                return ans;
            }
            w_n -= words[r].size() + 1;
            if (l + 1 == r) {
                str = words[l];
                str += string(maxWidth - str.size(), ' ');
                ans.push_back(str);
                continue;
            }
            string s((maxWidth - w_n) / (r - l - 1) + 1, ' ');
            str = words[l];
            for (int k = 1, n = (maxWidth - w_n) % (r - l - 1); k + l < r; ++k) {
                if (k <= n) str += " " + s + words[l + k];
                else str += s + words[l + k];
            }
            ans.push_back(str);
        }
    }
};